December i6, 1887.] 



SCIENCE 



293 



temperature off the west coasts of California and South America. A 

 number of protiles showing the temperatures of the Pacific Ocean 

 off the coast of California, which were published by Dr. C. M. 

 Richter in the Bulletin of the California Academy of Sciences, show 

 very plainly the rising of cold water near the shore ; and although 

 the author tries to prove, by means of these charts and profiles, the 

 existence of a cold current, they seem to be far more in favor of the 

 theory advanced above. 



It will be seen that in the equatorial parts of the Atlantic Ocean 

 two regions of remarkably cold water occur. One of these is on 

 the coast of Guinea ; the other, east of St. Paul. Krummel be- 

 lieves that they are also due to a submarine source, the cold water 

 of the depth taking the place of the warm dense water which is 

 driven westward by the wind. He points out that it is situated 

 between the equatorial current and the counter equatorial current, 

 and that thus the cold water supplies a deficiency caused by two 

 currents flowing in opposite directions. Therefore this area of cold 

 water does not exist in February, when both currents are less 

 strong. The Guinea current he considers entirely caused by the 

 southern equatorial current, and as supplying the Gulf of Guinea 

 with water instead of that which is drawn from it by the southern 

 equatorial current. We ought to point out here the fact shown by 

 Buchanan, that all counter equatorial currents are very superficial, 

 that their velocity is the greater the less the density of this 

 water, and that the isothermal gradients are very great below these 

 currents, as the light water of the surface prevents the heat from 

 penetrating into the ocean. 



The problems of the equatorial circulation of the oceans is ex- 

 tremely complicated, and the observations mentioned above show 

 that the vertical as well as the horizontal circulation of the waters 

 must be studied. The dynamics of the counter equatorial current 

 are particularly obscure, and a careful investigation of its density, 

 temperature, and strength is very desirable. 



MENTAL SCIENCE. 



The Mechanism of Attention.' 



Voluntary attention is an artificial act : it grafts itself upon 

 spontaneous attention, and takes its nourishment from this. In 

 spontaneous attention the object acts by its intrinsic power; in 

 voluntary attention the subject brings an alien power to bear upon 

 the process. Spontaneous attention represents the maximum of 

 attraction between .subject and object ; voluntary attention, the 

 maximum of resistance. It is the voluntary form of attention that 

 is here to be considered. 



in the first place, how is so artificial a process as voluntary at- 

 tention brought about ? The method, says M. Ribot, is to make 

 attractive artificially what is not so naturally ; to arouse an artificial 

 interest in things naturally uninteresting. The process by which this 

 is done is infinitely varied, but consists always of arousing an in- 

 terest by playing upon some emotional state. 



The infant, according to Preyer, at first is under the sway of 

 spontaneous attention alone : it looks only at bright objects, at 

 sustenance-giving objects. At about the end of the third month 

 it explores the field of vision, and glances at less and less (selfishly) 

 interesting objects ; and it is the same with the other senses. The 

 path is from the most intense, most impressive sensations to the 

 finer, more delicate ones. The child naturally flits from one sen- 

 sation to another : to fixate and hold one sensation is an art that 

 must be learned. A child, for example, refuses to learn to read, 

 but is vastly interested in the pictures in the book. The father says 

 that reading will show the meaning of the pictures. This acts as 

 an artificial inducement, and the child goes to work, substituting 

 an artificial attention to arbitrary signs for the natural attractiveness 

 of pictures. M. Ribot distinguishes three periods in this substitu- 

 tion process. In the first we can appeal to bodily feelings alone. 

 The child can be taught voluntary attention only by playing upon 

 its fear, its egoistic tendencies, by rewards, sympathetic emotions, 

 natural curiosity. In the second period the emotional nature is still 

 the most powerful motive, but the kind of emotion is higher. One 

 can here appeal to ambition, to emulation, to duty. In the final 

 period the attention is maintained by habit. The student at his 



1 A ritsum^ of an article by Prof. Th. Ribot (v. Scieni^ey No. 252). 



desk, the workman at his shop, often wish they were elsewhere ; 

 but the habit as formed by past appeals to pride, ambition, etc., 

 chains them to their tasks. Art has done its work, and attention 

 has become second nature. Granted a certain environment, and 

 the work goes on almost of itself. Many persons never reach this 

 third organized stage of voluntary attention : there is a vast body 

 of unsteady, Bohemian, vagabond types of character in whom volun- 

 tary attention is sporadic only, and not habitual. 



The training of animals proceeds by the same steps. An ape is 

 taught to do things meaningless to it by connecting such acts with 

 rewards and punishments. The factor of attention in the process is 

 well shown, in that such animals are selected for training as most 

 readily attend amid distractions. 



The genesis of voluntary attention is to be found in its utility. 

 When the conditions of life become at all hard, and especially if 

 they become so by more or less sudden changes, the power of 

 adaption to them is dependent upon voluntary attention to details ; 

 upon consideration of something besides the immediately attractive 

 and useful. The savage is lazy, is inspired only by chase, by war, 

 by play; his interest is in the unknown, the unforeseen, the chance. 

 He is not capable of continuous labor. In half-civilized com- 

 munities work is repugnant. Voluntary attention is a factor of civi- 

 lization, and is maintained with effort. The most constant char- 

 acteristic of criminals is lack of power to pursue a steady calling ; 

 and the Italian anthropologists regard this as a reversion to primitive 

 habits. Voluntary attention thus came in, and is maintained as a 

 sociological power. 



While we all have quite a definite notion of the feeling of effort 

 in fixing the attention, the nature of the process escapes our obser- 

 vation. We feel that the struggle is to focus the thought upon one 

 topic to the exclusion of others, all knocking for admittance into 

 consciousness. The question is not, ' How does a concept come to 

 be attended to ? ' but ' How is it maintained in the focus of atten- 

 tion? How do we inhibit other concepts?' The answer is very 

 incomplete. The physiology of inhibition is in its infancy. The 

 fact itself simply states that the excitation of a nerve may not only 

 produce motion, but may cause a motion to cease. Stimulating the 

 pneumogastric nerve arrests the heart-beat. The highest form of 

 this power of inhibition is attention : this Ferrier locates in the frontal 

 lobes of the brain. The intelligence would thus be proportionate to 

 the development of these lobes ; stimulation of them would never pro- 

 duce movements ; and their disease would cause no paralysis, but a 

 lowering of the mental life. All this is found to be true. Inhibition 

 is likewise late in appearing, coming long after impulsive will in 

 child-development. We know only the initial and final steps of the 

 process, the will not to do an action, the fact that it is not done ; 

 but we have good reason to believe that the muscles play an active 

 role in the process. 



Attention may be fixed upon three kinds of mental objects, — 

 perceptions, images, ideas. In perception the dominance of the 

 motor element is evident. In seeing, touching, etc., there is always 

 a motion ; and the law that the more mobile the part the more 

 sensitive it is, is quite a general one. To fixate an object steadily 

 without moving the eye soon reduces the field of vision to a blank ; 

 a weight constantly pressing upon the skin is soon not felt. Con- 

 sciousness is always of change, and change is based upon move- 

 ment. Attention is the repression of foreign, irrelevant movements 

 and the concentration upon pertinent ones. Distraction is a dif- 

 fusion of movements. Next with regard to images. Here the 

 attention is turned inwards, and becomes reflection; but the motor 

 element has not been lost. The motor element of the perception is 

 only weakened (not lost) in its recollection. The two processes 

 are the same in kind, and differ only in degree. As the vividness 

 of the recollection increases, it approaches the perception in the 

 prominence of the motor element. The intense thought of falling 

 down an abyss has led some persons to throw themselves down. 

 Mind-reading is really muscle-reading. When we pass to ideas 

 (and especially abstract ideas), the problem is more difficult. M. 

 Ribot confines his attention to three types of ideas. The first are 

 such as are formed by the fusion of like images without the aid of a 

 word. Their type is the idea of a class, a species. This is within 

 the grasp of animals, children, and deaf-mutes. It is a generic 

 image, like a composite portrait. Here the question as to the motor 



